[5.x] schemaorg recipe: Output absolute image URLs and support ImageObject

[manuelkling]

The schemaorg Recipe plugin currently outputs the image as a relative path. This is not ideal for search engines: Rich Results expect a publicly reachable HTTP(S) URL.

Expected:

• Recipe.image uses absolute HTTP(S) URL, or an ImageObject with url/width/height.

Actual:

• Image is emitted as joomlaImage with relative path tied to Joomla's media system.

Proposal:

• Resolve media field to a public absolute URL
• Prefer emitting an ImageObject with width/height taken from the media metadata.

[brianteeman]

Related #43955

[richard67]

Closing as having a pull request. Please test #46306 . Thanks in advance.